Ribbed concrete slab

ABSTRACT

The invention relates to a ribbed concrete slab, the slab of which is prolonged in its longitudinal direction beyond the two ends of the rib in order to form a bearing in each case, and in order to reinforce the said bearing an additional reinforcement is provided extending into the bearing and arranged in the region of the rib.

Unlted States Patent 1 1 1111 3,800,491

Gunia Apr. 2, 1974 [541 RIBBED CONCRETE SLAB 3,243,927 4/1966 Hilson 52/157 3,487,597 1/1970 Gutt 52/204 Inventor g Gum, Rhme 3,605,353 9 1971 Marcott 52/600 ermany FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Friedr. Remy Nachfolger KG, In der Sohl Germany 1,105,452 7/1955 France 1. 52/600 450,489 7/1949 Italy 52/260 [22] Filed: Nov. 24, 1971 Primary Examiner-Henry C. Sutherland [211 App]. No" 201,811 Assistant Examiner.lames L. Ridgill, Jr.

' Attorney, Agent, or Firm-Woodhams, Blanchard & [30] Foreign Application Priority Data Flynn Nov. 28, 1970 Germany 2058714 57 ABSTRACT [52] US. Cl. .1 52/602, 52/610 51 1m. (:1. E04b 5/04, E040 2/06 The memo relates to a "bbed Concrete Slab, the 5 i l f Search M 52/ 0 01 260 204 slab of which iS prolonged in its longitudinal direction 52/157, 653, 602, 608, 609, 610 beyond the two ends of the rib in order to form a bearing in each case, and in order to reinforce the said [56] References Cited bearing an additional reinforcement is provided ex- UNITED STATES PATENTS tending into the bearing and arranged in the region of the rib. 1,205,465 11/1916 Maguire et a1 52/236 871,075 12/1907 Swensson 52/653 7' Claims, 10 Drawing Figures PATENTEDAPR 21914 3.800.491

IN VEN TOR W! 445' 6' 4/4 04 PATENTEDAPR 2 I974 SHEET l- UF 6 INVENTOR AZ AA /6 G'/A/M BY RIBBED CONCRETE SLAB In one known ribbed slab of this type, according to DIN 1045 an additional bearing reinforcement is provided which comprises a plurality of steel reinforcing bars, but in this case it is difficult to accommodate the said steel reinforcing bars within the relatively thin slab and also to maintain the correct position of the steel bars, so that faulty products are frequently obtained for this reason. A ribbed slab with this additional reinforcement is also inadequate from static considerations, because the main reinforcement consists solely of a round steel stirrup bent into a U-shape, which is arranged in the bearing in such a way that the one arm of the said stirrup extends into the slab, whereas the other stirrup arm is bent obliquely downwards from the bearing and its end is arranged in the lower part of the rib. In spite of the considerable outlay of material and labour costs,

this bearing reinforcement has an inadequate load bearing capacity, so that cracking or fracture occurs at the bearing in the case of fairly long ribbed concrete slabs or under fairly high loads.

It is the underlying aim of the invention to eliminate the above stated disadvantages and to produce a ribbed concrete slab with a bearing reinforcement which makes possible a substantial economy of material and considerable reduction in labour costs and also results in a substantially higher load bearing capacity whilst avoiding cracking.

In order to achieve this aim a ribbed concrete slab of the initially defined mode of construction is provided, the additional bearing reinforcement of which according to the invention comprises one or a plurality of straight cantilever beams arranged in the slab in its Iongitudinal direction and at least one tie rod arranged in proximity of the end of the rib, which is arranged in a plane oriented perpendicularly to the cantilever beams and which connects the cantilever beams tensionally to the lower longitudinal reinforcement of the rib.

The invention is explained in further detail hereinbelow with reference to exemplary embodiments illustrated in the drawing, wherein:

FIG. 1 shows in plan a ribbed slab with slab reinforcement and bearing reinforcement;

FIG. 2 shows a longitudinal section taken along the line ll/Il of FIG. 1;

FIG. 3 shows a cross section along the III/III of FIG.

FIG. 4 shows a cross section along the line IV/IV of FIG.1;

FIGS. 5 to 7 show another embodiment of the bearing reinforcement of a ribbed concrete slab illustrated similarly to FIGS. 1 to 3;

FIG. 8 shows a third embodiment in cross section (according to FIG. 3);

FIG. 9 the bearing reinforcement of a Pi-shaped slab;

FIG. 10 shows a truss with bearing and bearing reinforcement according to the invention.

The FIGS. 1 to 4, and also 5 to 7, illustrate a ribbed slab having an L-shaped cross section which comprises a slab l and a rib 2 which is arranged at one longitudinal side of the slab. On this longitudinal side the slab also has a recess 3 which serves (see FIG. 4) for the purpose of placing the said ribbed slabs together and mutually bracing them. Ribbed slabs of this type are used as floor slabs or roof slabs.

The slabs 1 are also (see FIGS. 1 2, 5, 6) prolonged beyond both the rib ends 4 in order to form a bearing 5 arranged at each of the end faces of the slab. The ribbed slab is supported by the said bearing upon a truss 6. In order to absorb the bearing forces effectively, an additional reinforcement is provided in the ribbed slab, comprising one or a plurality of cantilever beams 7a to 7d (FIGS. 1 to 3) or 8a, 8b (FIGS. 5 to 7) arranged straight in the slab 1 in its longitudinal direction and having at least a pair of opposed vertically opposed upstanding laterally facing wall surfaces extending parallel to the longitudinal direction to resist deflections of the beams about an axis perpendicular to the wall surfaces, and at least one tie rod 9a, 9b or 10a which is arranged in proximity of the rib end 4 and is arranged in a plane oriented perpendicularly to the cantilever beams 7a to 7d or 8a, 8b, and which connect the said cantilever beams tensionally to the lower longitudinal reinforcement 11 of the rib. In the embodiment according to FIGS. 1 to 3, the cantilever beams 7a to 7d consist of strip steel, and in fact advantageously of a single, multiply bent steel strip placed on edge which has a plurality of horizontal ribs 12 stamped out of the said steel strip. These ribs are provided for the purpose of better absorption of the shear forces between concrete and steel strip and to achieve a more intimate .connection between the concrete and the cantilever beams. The tie rods 9a, 9b are constructed as a stirrup (see FIG. 3) which embraces the rib reinforcement 11. The arm ends 13 may be made hook shaped so that they rest upon the cantilever beams 7 and thus connect the said cantilever beams tensionally to the rib reinforcements 11. The forces exerted upon the cantilever beamsat the bearing 5 are therefore transmitted by the said tie rods to the rib 2 and to its reinforcement 11, so that the load bearing capacity is considerably increased in this way and cracking in the bearing is avoided. In order to ensure such a tensile connection between cantilever beams and rib reinforcement, the ends of the tie stirrups 9 are conveniently welded to the cantilever beams.

As may be seen from the drawing, the length 1 of the cantilever beams 7 or 8 present in the slab l is equal to three or four times the length l, of the cantilever arm present in the bearing 5.

In the embodiment according to FIGS. 1 to 4, a known filigree beam is provided as reinforcement of the rib 2, and comprises the longitudinal reinforcement 11 (bottom flange), a top flange (l4) and a zig-zag shaped round steel bar 15, these parts of the beam being attached to each other by welding. Longitudinal reinforcements l6 and transverse reinforcements 17 are provided for the bay reinforcement of the slab 1.

In the advantageous embodiment according to FIGS. 5 to 7, the cantilever beams arranged in this slab 1 consist of U-shaped profiles 8a, 8b, which are conveniently arranged in pairs, and the tie rods 10a, 10b consist of strip steel stirrups, the ends 18 of which are inserted between the U-shaped profiles 8a, 8b and are attached to the webs of the said U-shaped profiles by welding. These U-shaped profiles in the arrangement illustrated have a high moment of resistance in proportion to the material outlay, so that the flexural forces indicated by the arrow A (FIG. 6) which occur at the bearing are effectively absorbed. Since the concrete enters between the flanges of the U-shaped profiles, in this way an intimate bond is achieved between the concrete and the cantilever beams, effectively absorbing the shear forces. The bottom flanges of these U-shaped profiles produce a larger surface on the bearing, with the result that the specific surface pressure on the bearing is reduced, consequently no damage to or failure of the concrete on the bearing can occur due to this bearing pressure. According to FIGS. 5 and 6, besides the tie rod a provided in proximity of the rib end 4, there is provided at the ends of the cantilever beams 8a, 8b a further tie rod which firmly connects the cantilever beams to the rib reinforcements l 1. In order to form as rigid as possible a bearing reinforcement, which eliminates any variation in shape due to the bearing forces, the two tie rods 10a, 10b may advantageously be further mutually connected by diagonal tension members 19, as indicated by chain dotted lines in FIG. 6. Again in the case of this reinforcement according to FIGS. 5 to 7, the previously described filigree beam may be provided as rib reinforcement. Furthermore, instead of U- shaped profiles for the cantilever beams, other profiles e.g. Z-shaped profiles may also be provided.

FIG. 8 illustrates that, if desired, it is also possible for only a single cantilever beam e.g. constructed as a U-shaped profile to be provided in the slab 1. Also the tie rod which connects the said cantilever beam to the rib reinforcements 11 may also be constructed, as illustrated, as a loop 21 which wraps both the cantilever beam 20 and also the reinforcement 11.

FIG. 9 illustrates that the additional bearing reinforcement according to the invention may also be provided in the case of a Pi-shaped slab which comprises a slab 22 and the two longitudinal ribs 23. The end faces of the slab 22 protrude beyond the ends 24 of the ribs and form a bearing 25 for supporting the said Pishaped slab on a truss. The additional bearing reinforcement consists of the U-shaped profiles 26 provided as cantilever beams, which are tensionally connected to the rib reinforcements l l by tie rods 10a, 10b in the sense of the embodiment previously described (FIGS. 5 to 7).

FIG. 10 illustrates that the invention is also applicable in the case of reinforced concrete trusses, the top flange 27 of which protrudes beyond the web end 23 of the said truss and forms a projecting bearing at 29. In the sense of the invention, here again cantilever beams consisting of U-shaped profiles 30 or the like are provided arranged in the top flange 27 and extending into the bearing 29, and are tensionally attached to the web reinforcements 31 by tie rods 10a, 10b.

The bearing reinforcement according to the invention produces high load bearing capacity for a minimum material outlay. It also has the advantage that the novel bearing reinforcement constitutes a unit connected by welding etc. which can be maintained in the correct position without difficulty and satisfactorily during the pouring of the ribbed slab. The novel bearing reinforcement also makes possible an ideal absorption of the shear forces within the bearing, since the total cross section of the cantilever beams is present in every sectional position.

In order to constitute the above mentioned unit, the cantilever beams are conveniently firmly attached together in the horizontal direction by transverse steel members 32, as illustrated by way of example in FIGS. 5, 6.

In the case of a ribbed slab according to FIGS. 5 to 7, which has a thickness 5 of mm, for example U- profile cantilever beams 8a, 8b of 40 X 20 mm and with a length of 400 mm may be provided as additional bearing reinforcement, and steel strips of 30 X 3 mm may be provided for the tie rods 10a, 10b. In this case the bearing 5 protrudes by the dimension a of approximately mm beyond the rib end face 4, while the rib 2 has a height h of 210 mm.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An elongated ribbed concrete slab of finite length having at least one rib extending downwardly therefrom and extending parallel to the longitudinal axis of said concrete slab, comprising:

at least one cantilever portion on said concrete slab extending in the longitudinal direction beyond the end of said rib to define a cantilever bearing structure at said end and adapted to engage and rest on a truss member;

reinforcing means consisting of at least one elongated cantilevered beam embedded in said slab and having a longitudinal axis parallel to said longitudinal axis of said concrete slab and a longitudinal part extending into said cantilever bearing structure, said cantilevered beam consisting of a single multiple bent steel strip placed on edge and having a plurality of horizontal ribs punched out from said steel strip, at least one elongated reinforcement member positioned in said rib below and parallel to said cantilevered beam and at least one tie rod adjacent said end of said rib and connecting said cantilevered beam to said reinforcement member, said tie rod lying in a plane generally perpendicular to said longitudinal direction of said cantilevered beam.

2. An elongated ribbed concrete slab of finite length having at least one rib extending downwardly therefrom and extending parallel to the longitudinal axis of said concrete slab, comprising:

at least one cantilever portion on said concrete slab extending in the longitudinal direction beyond the end of said rib to define a cantilever bearing structure at said end and adapted to engage and rest on a truss member; reinforcing means consisting of at least one elongated cantilevered beam embedded in said slab and having a longitudinal axis parallel to said longitudinal axis of said concrete slab and a longitudinal part extending into said cantilever bearing structure, said cantilevered beam consisting of a beam member having means thereon defining at least a pair of connected and opposed vertically upstanding laterally facing wall surfaces extending parallel to said longitudinal axis of said concrete slab and adapted to specifically resist deflections of said beam member at least about an axis perpendicular to said wall surfaces, at least one elongated reinforcement member positioned in said rib below and parallel to said cantilevered beam and at least one tie rod adjacent said end of said rib and connecting said cantilevered beam to said reinforcement member, said tie rod lying in a plane generally perpendicular to said longitudinal direction of said cantilevered beam.

3. A ribbed slab according to claim 2, wherein the length (1 of said beam member in the slab is in the strip which is connected to the webs of said one of said U-shaped and Z-shaped profiles by welding.

6. A ribbed slab according to claim 2, wherein the ends of the cantilever beam are connected to the reinforcement members by a further tie rod.

7. A ribbed slab according to claim 6, wherein the two tie rods are mutually connected by a diagonal tension members. 

1. An elongated ribbed concrete slab of finite length having at least one rib extending downwardly therefrom and extending parallel to the longitudinal axis of said concrete slab, comprising: at least one cantilever portion on said concrete slab extending in the longitudinal direction beyond the end of said rib to define a cantilever bearing structure at said end and adapted to engage and rest on a truss member; reinforcing means consisting of at least one elongated cantilevered beam embedded in said slab and having a longitudinal axis parallel to said longitudinal axis of said concrete slab and a longitudinal part extending into said cantilever bearing structure, said cantilevered beam consisting of a single multiple bent steel strip placed on edge and having a plurality of horizontal ribs punched out from said steel strip, at least one elongated reinforcement member positioned in said rib below and parallel to said cantilevered beam and at least one tie rod adjacent said end of said rib and connecting said cantilevered beam to said reinforcement member, said tie rod lying in a plane generally perpendicular to said longitudinal direction of said cantilevered beam.
 2. An elongated ribbed concrete slab of finite length having at least one rib extending downwardly therefrom and extending parallel to the longitudinal axis of said concrete slab, comprising: at least one cantilever portion on said concrete slab extending in the longitudinal direction beyond the end of said rib to define a cantilever bearing structure at said end and adapted to engage and rest on a truss member; reinforcing means consisting of at least one elongated cantilevered beam embedded in said slab and having a longitudinal axis parallel to said longitudinal axis of said concrete slab and a longitudinal part extending into said cantilever bearing structure, said cantilevered beam consisting of a beam member having means thereon defining at least a pair of connected and opposed vertically upstanding laterally facing wall surfaces extending parallel to said longitudinal axis of said concrete slab and adapted to specifically resist deflections of said beam member at least about an axis perpendicular to said wall surfaces, at least one elongated reinforcement member positioned in said rib below and parallel to said cantilevered beam and at least one tie rod adjacent said end of said rib and connecting said cantilevered beam to said reinforcement member, said tie rod lying in a plane generally perpendicular to said longitudinal direction of said cantilevered beam.
 3. A ribbed slab according to claim 2, wherein the length (12) of said beam member in the slab is in the range of from three to four times the length (11) of said longitudinal part of said beam member present in said bearing structure.
 4. A ribbed slab according to claim 2, wherein the tie rod defines a stirrup which embraces the reinforcement member.
 5. A ribbed slab according to claim 4, wherein said beam member comprises one of a U-shaped or a Z-shaped profile arranged in pairs and lying in a horizontal plane, and wherein said tie rod consists of a steel strip which is connected to the webs of said one of said U-shaped and Z-shaped profiles by welding.
 6. A ribbed slab according to claim 2, wherein the ends of the cantilever beam are connected to the reinforcement members by a further tie rod.
 7. A ribbed slab according to claim 6, wherein the two tie rods are mutually connected by a diagonal tension members. 